These studies have clarified the relationship between postoperative hemodynamic function, the development of ARF and the lethality of postoperative ARF. In addition, the demonstration of tubular back-leakage of glomerular filtrate provided an important insight into the renal pathophysiological mechanisms involved. A measurement set useful for rapid monitoring of postoperative renal function has been defined. Finally, the analysis of the relationship of ARF to CPB with low flow pressure raised important questions about the critical determinants of microcirulatory adequacy during CPB. Answers to these questions should provide important information about microcirculatory function in general. RESEARCH GOALS FOR THE NEXT YEAR: 1. A comprehensive analysis of the renal pathophysiological changes which characterize evolving, established and resolving phases of ARF in man. Determination of the time of resolution of tubular back-leakage of glomerular filtrate in patients recovering from ARF. 2. Analysis of the renal functional effects of renal ischemia in patients undergoing suprarenal clamping for aortic or renal vascular surgery. Comparison of the characteristics of ARF in these patients to the cardiac surgical patients and to the numerous animal modula so extensively investigated will be useful. 3. Determination of renal function during, and after, cardiac surgery. A comparison of the renal functional effects of routine mannitol adminstration, manitol adminstration prior to CPB, and high dose mannitol administration will be performed. 4. Pilot studies in experimental animals to determine the effects of CPB upon renal mitochondrial redox state will be performed under varying conditions of flow and pressure. Precise information on renal oxygenation during CPB will be important in clarifying our results to date.